Marine biodiversity characteristics

Oceans contain the largest living volume of the “blue” planet, inhabited by approximately 235–250,000 described species, all groups included. They only represent some 13% of the known species on the Earth, but the marine biomasses are really huge. Marine phytoplankton alone represents half the production of organic matter on Earth while marine bacteria represent more than 10%. Life first appeared in the oceans more than 3.8 billion years ago and several determining events took place that changed the course of life, ranging from the development of the cell nucleus to sexual reproduction going through multi-cellular organisms and the capture of organelles. Of the 31 animal phyla currently listed, 12 are exclusively marine phyla and have never left the ocean. An interesting question is to try to understand why there are so few marine species versus land species? This pattern of distribution seems pretty recent in the course of Evolution. From an exclusively marine world, since the beginning until 440 million years ago, land number of species much increased 110 million years ago. Specific diversity and ancestral roles, in addition to organizational models and original behaviors, have made marine organisms excellent reservoirs for identifying and extracting molecules (> 15,000 today) with pharmacological potential. They also make particularly relevant models for both fundamental and applied research. Some marine models have been the source of essential discoveries in life sciences. From this diversity, the ocean provides humankind with renewable resources, which are highly threatened today and need more adequate management to preserve ocean habitats, stocks and biodiversity.     

New species in the Old World: Europe as a frontier in biodiversity exploration, a test bed for 21st century taxonomy

The number of described species on the planet is about 1.9 million, with ca. 17,000 new species described annually, mostly from the tropics. However, taxonomy is usually described as a science in crisis, lacking manpower and funding, a politically acknowledged problem known as the Taxonomic Impediment. Using data from the Fauna Europaea database and the Zoological Record, we show that contrary to general belief, developed and heavily-studied parts of the world are important reservoirs of unknown species. In Europe, new species of multicellular terrestrial and freshwater animals are being discovered and named at an unprecedented rate: since the 1950s, more than 770 new species are on average described each year from Europe, which add to the 125,000 terrestrial and freshwater multicellular species already known in this region. There is no sign of having reached a plateau that would allow for the assessment of the magnitude of European biodiversity. More remarkably, over 60% of these new species are described by non-professional taxonomists. Amateurs are recognized as an essential part of the workforce in ecology and astronomy, but the magnitude of non-professional taxonomist contributions to alpha-taxonomy has not been fully realized until now. Our results stress the importance of developing a system that better supports and guides this formidable workforce, as we seek to overcome the Taxonomic Impediment and speed up the process of describing the planetary biodiversity before it is too late.     

Current problems in marine biodiversity studies

This paper deals with a discussion of terminology and six proposed levels of biodiversity. Recent data and estimates were used to compare species and taxonomic diversity of terrestrial, freshwater, and marine organisms. About 1.5 million terrestrial species and 320000 aquatic species are hitherto known. In spite of a long history of research, only about 280000 marine species have been discovered, of which 180000 species are invertebrates. Of 33 metazoan phyla, 31 are found in the sea, 13 of these being exclusively marine. Seventeen metazoan phyla contain freshwater species, and only 11 phyla comprise terrestrial animals. Two phyla (freshwater Micrognathozoa and terrestrial Onychophora) possess no marine species. In this paper, we review the assessment reports on marine biological diversity in coral reefs, coastal ecosystems, macrobenthos, and meiofauna. Recent data on the number of known species are listed for each metazoan phylum; the number of anticipated new species to be discovered is estimated. Deep-sea macrobenthos are believed to comprise about 25 million species; meiofauna seems to be composed of 20 to 30 million species, ten million of whom are marine nematodes. Hypotheses are discussed that can account for the high species diversity of deep-sea macrobenthos and meiofauna.     

Epidemiology and potential land-sea transfer of enteric bacteria from terrestrial to marine species in the Monterey Bay Region of California

Marine mammals are at risk for infection by fecal-associated zoonotic pathogens when they swim and feed in polluted nearshore marine waters. Because of their tendency to consume 25-30% of their body weight per day in coastal filter-feeding invertebrates, southern sea otters (Enhydra lutris nereis) can act as sentinels of marine ecosystem health in California. Feces from domestic and wildlife species were tested to determine prevalence, potential virulence, and diversity of selected opportunistic enteric bacterial pathogens in the Monterey Bay region. We hypothesized that if sea otters are sentinels of coastal health, and fecal pollution flows from land to sea, then sea otters and terrestrial animals might share the same enteric bacterial species and strains. Twenty-eight percent of fecal samples tested during 2007-2010 were positive for one or more potential pathogens. Campylobacter spp. were isolated most frequently, with an overall prevalence of 11%, followed by Vibrio cholerae (9%), Salmonella spp. (6%), V. parahaemolyticus (5%), and V. alginolyticus (3%). Sea otters were found positive for all target bacteria, exhibiting similar prevalences for Campylobacter and Salmonella spp. but greater prevalences for Vibrio spp. when compared to terrestrial animals. Fifteen Salmonella serotypes were detected, 11 of which were isolated from opossums. This is the first report of sea otter infection by S. enterica Heidelberg, a serotype also associated with human clinical disease. Similar strains of S. enterica Typhimurium were identified in otters, opossums, and gulls, suggesting the possibility of land-sea transfer of enteric bacterial pathogens from terrestrial sources to sea otters.     

Expansion dating: calibrating molecular clocks in marine species from expansions onto the Sunda Shelf Following the Last Glacial Maximum

The rate of change in DNA is an important parameter for understanding molecular evolution and hence for inferences drawn from studies of phylogeography and phylogenetics. Most rate calibrations for mitochondrial coding regions in marine species have been made from divergence dating for fossils and vicariant events older than 1-2 My and are typically 0.5-2% per lineage per million years. Recently, calibrations made with ancient DNA (aDNA) from younger dates have yielded faster rates, suggesting that estimates of the molecular rate of change depend on the time of calibration, decaying from the instantaneous mutation rate to the phylogenetic substitution rate. aDNA methods for recent calibrations are not available for most marine taxa so instead we use radiometric dates for sea-level rise onto the Sunda Shelf following the Last Glacial Maximum (starting ～18,000 years ago), which led to massive population expansions for marine species. Instead of divergence dating, we use a two-epoch coalescent model of logistic population growth preceded by a constant population size to infer a time in mutational units for the beginning of these expansion events. This model compares favorably to simpler coalescent models of constant population size, and exponential or logistic growth, and is far more precise than estimates from the mismatch distribution. Mean rates estimated with this method for mitochondrial coding genes in three invertebrate species are elevated in comparison to older calibration points (2.3-6.6% per lineage per million years), lending additional support to the hypothesis of calibration time dependency for molecular rates.     

Ocean and bio-medical research

On the Planet Earth, oceans and seas today correspond to the largest volume offered to Life. Roughly, 275,000 species have been described from marine environments, only representing some 15% of all the present known living. But marine biomass can be enormous. Life appeared in the ancestral ocean 3 800 million years ago and determining events occurred there: appearance of the nuclear membrane and cell nucleus, "pluricellularity", capture of bacteria transformed into organelles, then sexuality. On the 33 phyla existing today on the Earth, 12 never have left the ocean and are exclusively marine. Such biodiversity, archaism of characters, organisational and behavioural patterns make these marine organisms an excellent reservoir for identifying and extracting very interesting pharmacological and cosmetic molecules (>5 000 today) and/or to represent very pertinent "models" for basic and applied research. Relationships between ocean and public health are physical, chemical, biological and physiological. A few marine species as "models" set the base for major advances in life sciences recognized by several Nobel Prices: from the discovery of phagocytosis to anaphylactic shock, and including nervous influx transmission, memory molecular bases, cyclins discovery, eye organisation, neurotransmitter membrane receptors, bases of the specific immune system... These marine models are very useful to understand the origin and functioning of important living mechanisms in the human and sometimes to deduce applications for efficient treatments. Ocean supplies mankind with renewable living resources, much threatened today. We have to manage and protect these to maintain ecosystems, stocks and biodiversity. Only because of the greenhouse effect and anthropic emissions, temperature is globally increasing: and, what if (tomorrow?) one million species would disappear (before 2050) because of global warming?     

Effects of experimental warming on biodiversity depend on ecosystem type and local species composition

Climatic warming is a primary driver of change in ecosystems worldwide. Here, we synthesize responses of species richness and evenness from 187 experimental warming studies in a quantitative meta‐analysis. We asked 1) whether effects of warming on diversity were detectable and consistent across terrestrial, freshwater and marine ecosystems, 2) if effects on diversity correlated with intensity, duration, and experimental unit size of temperature change manipulations, and 3) whether these experimental effects on diversity interacted with ecosystem types. Using multilevel mixed linear models and model averaging, we also tested the relative importance of variables that described uncontrolled environmental variation and attributes of experimental units. Overall, experimental warming reduced richness across ecosystems (mean log‐response ratio = –0.091, 95% bootstrapped CI: –0.13, –0.05) representing an 8.9% decline relative to ambient temperature treatments. Richness did not change in response to warming in freshwater systems, but was more strongly negative in terrestrial (–11.8%) and marine (–10.5%) experiments. In contrast, warming impacts on evenness were neutral overall and in aquatic systems, but weakly negative on land (7.6%). Intensity and duration of experimental warming did not explain variation in diversity responses, but negative effects on richness were stronger in smaller experimental units, particularly in marine systems. Model‐averaged parameter estimation confirmed these main effects while accounting for variation in latitude, ambient temperature at the sites of manipulations, venue (field versus lab), community trophic type, and whether experiments were open or closed to colonization. These analyses synthesize extensive experimental evidence showing declines in local richness with increased temperature, particularly in terrestrial and marine communities. However, the more variable effects of warming on evenness were better explained by the random effect of site identity, suggesting that effects on species’ relative abundances were contingent on local species composition. Synthesis A global research priority is to understand the consequences of climate change for biodiversity. A growing number of experimental studies have manipulated climatic drivers, in particular changes in temperature, in local communities. In the first quantitative meta‐analysis of community‐level studies across freshwater, marine and terrestrial experiments, species richness declined consistently with experimental warming. This effect was insensitive to warming intensity, duration, and multiple environmental and procedural covariates. However, evenness responses were weakly negative only in terrestrial systems and more variable across ecosystem types. Linear mixed model analyses revealed that the identity of local sites explained nearly 50% of variance in evenness effect sizes, compared to only 10% for richness. This result provides evidence that local species composition strongly constrains changes in relative species abundances in response to warming.     

Collembola,the biological species concept and the underestimation of global species richness

Despite its ancient origin, global distribution and abundance in nearly all habitats, the class Collembola is comprised of only 8000 described species and is estimated to number no more than 50 000. Many morphologically defined species have broad geographical ranges that span continents, and recent molecular work has revealed high genetic diversity within species. However, the evolutionary significance of this genetic diversity is unknown. In this study, we sample five morphological species of the globally distributed genus Lepidocyrtus from 14 Panamanian sampling sites to characterize genetic diversity and test morphospecies against the biological species concept. Mitochondrial and nuclear DNA sequence data were analysed and a total of 58 molecular lineages revealed. Deep lineage diversification was recovered, with 30 molecular lineages estimated to have established more than 10 million years ago, and the origin almost all contemporary lineages preceding the onset of the Pleistocene (~2 Mya). Thirty‐four lineages were sampled in sympatry revealing unambiguous cosegregation of mitochondrial and nuclear DNA sequence variation, consistent with biological species. Species richness within the class Collembola and the geographical structure of this diversity are substantially misrepresented components of terrestrial animal biodiversity. We speculate that global species richness of Collembola could be at least an order of magnitude greater than a previous estimate of 50 000 species.     

Biological control of marine invasive species: cautionary tales and land-based lessons

Biological control (biocontrol) has successfully regulated pest populations in terrestrial agroecosystems, but it has also caused negative unintended consequences for native species. Marine biologists and resource managers have recently published a growing number of proposals to include biocontrol in integrated pest management programs in oceans, seas and estuaries. Here, I review six ecologically and taxonomically diverse case studies of marine biocontrol programs at various stages of planning and implementation. Proposals include viral or microbial control of harmful algal blooms, predatory control of the ctenophore Mnemiopsis leidyi in the Black Sea, parasitic regulation of the European green crab Carcinus maenas, castration by ciliates of the seastar Asterias amurensis in Australia, herbivory of the toxic green alga Caulerpa taxifolia in the Mediterranean by sacoglossan sea slugs, and insect biocontrol by the planthopper Prokelesia marginata to ameliorate ecological impacts of the saltmarsh cordgrass Spartina alterniflora. Where data exist, I evaluate these examples in terms of lessons marine invasion biologists can glean from the rich history of terrestrial biocontrol, and explicitly contrast agroecosystems with invaded marine habitats. Host specificity cannot be guaranteed in the marine biocontrol proposals examined. Feasible alternatives to classical biocontrol in the marine realm should be emphasized, including more investment in invasion prevention tools, early detection and eradication while invasions are small, and increased attention to native natural enemies to control exotic pests. Biocontrol in marine habitats is risky: it poses many more uncertainties and has a much sparser history than its counterpart on land.     

Pushing the limits in marine species distribution modelling: lessons from the land present challenges and opportunities

Aim Species distribution models (SDMs) have been used to address a wide range of theoretical and applied questions in the terrestrial realm, but marine‐based applications remain relatively scarce. In this review, we consider how conceptual and practical issues associated with terrestrial SDMs apply to a range of marine organisms and highlight the challenges relevant to improving marine SDMs. Location We include studies from both marine and terrestrial systems that encompass many geographic locations around the globe. Methods We first performed a literature search and analysis of marine and terrestrial SDMs in ISI Web of Science to assess trends and applications. Using knowledge from terrestrial applications, we critically evaluate the application of SDMs in marine systems in the context of ecological factors (dispersal, species interactions, aggregation and ontogenetic shifts) and practical considerations (data quality, alternative modelling approaches and model validation) that facilitate or create difficulties for model application. Results The relative importance of ecological factors to be considered when applying SDMs varies among terrestrial and marine organisms. Correctly incorporating dispersal is frequently considered an important issue for terrestrial models, but because there is greater potential for dispersal in the ocean, it is often less of a concern in marine SDMs. By contrast, ontogenetic shifts and feeding have received little attention in terrestrial SDM applications, but these factors are important to many marine SDMs. Opportunities also exist for applying more advanced SDM approaches in the marine realm, including mechanistic ecophysiological models, where water balance and heat transfer equations are simpler for some marine organisms relative to their terrestrial counterparts. Main conclusions SDMs have generally been under‐utilized in the marine realm relative to terrestrial applications. Correlative SDM methods should be tested on a range of marine organisms, and we suggest further development of methods that address ontogenetic shifts and feeding interactions. We anticipate developments in, and cross‐fertilization between, coupled correlative and process‐based SDMs, mechanistic eco‐physiological SDMs, and spatial population dynamic models for climate change and species invasion applications in particular. Comparisons of the outputs of different model types will provide insight that is useful for improved spatial management of marine species.     

Marine invasions by non-sea snakes, with thoughts on terrestrial-aquatic-marine transitions

Few species of snakes show extensive adaptations to aquatic environments and even fewer exploit the oceans. A survey of morphology, lifestyles, and habitats of 2552 alethenophidian snakes revealed 362 (14%) that use aquatic environments, are semi-aquatic, or aquatic; about 70 (2.7%) of these are sea snakes (Hydrophiinae and Laticaudinae). The ancient and aquatic family Acrochordidae contains three extant species, all of which have populations inhabiting brackish or marine environments, as well as freshwater. The Homalopsidae have the most ecologically diverse representatives in coastal habitats. Other families containing species exploiting saline waters with populations in freshwater environments include: the Dipsadidae of the western hemisphere, the cosmopolitan Natricidae, the African Grayinae, and probably a few Colubridae. Species with aquatic and semi-aquatic lifestyles are compared with more terrestrial (fossorial, cryptozoic, and arboreal) species for morphological traits and life histories that are convergent with those found in sea snakes; this may provide clues to the evolution of marine snakes and increase our understanding of snake diversity.     

How many species of flowering plants are there?

We estimate the probable number of flowering plants. First, we apply a model that explicitly incorporates taxonomic effort over time to estimate the number of as-yet-unknown species. Second, we ask taxonomic experts their opinions on how many species are likely to be missing, on a family-by-family basis. The results are broadly comparable. We show that the current number of species should grow by between 10 and 20 per cent. There are, however, interesting discrepancies between expert and model estimates for some families, suggesting that our model does not always completely capture patterns of taxonomic activity. The as-yet-unknown species are probably similar to those taxonomists have described recently—overwhelmingly rare and local, and disproportionately in biodiversity hotspots, where there are high levels of habitat destruction.     

Uncoupling ecological innovation and speciation in sea snakes (Elapidae, Hydrophiinae, Hydrophiini)

The viviparous sea snakes (Hydrophiini) are by far the most successful living marine reptiles, with ～ 60 species that comprise a prominent component of shallow-water marine ecosystems throughout the Indo-West Pacific. Phylogenetically nested within the ～ 100 species of terrestrial Australo-Melanesian elapids (Hydrophiinae), molecular timescales suggest that the Hydrophiini are also very young, perhaps only ～ 8-13 Myr old. Here, we use likelihood-based analyses of combined phylogenetic and taxonomic data for Hydrophiinae to show that the initial invasion of marine habitats was not accompanied by elevated diversification rates. Rather, a dramatic three to six-fold increase in diversification rates occurred at least 3-5 Myr after this transition, in a single nested clade: the Hydrophis group accounts for ～ 80% of species richness in Hydrophiini and ～ 35% of species richness in (terrestrial and marine) Hydrophiinae. Furthermore, other co-distributed lineages of viviparous sea snakes (and marine Laticauda, Acrochordus and homalopsid snakes) are not especially species rich. Invasion of the oceans has not (by itself) accelerated diversification in Hydrophiini; novelties characterizing the Hydrophis group alone must have contributed to its evolutionary and ecological success.     

海洋外来物种入侵生态学研究

海洋外来物种入侵已成为最为严重的全球性环境问题之一。海洋生态系统类型多样、环境复杂,其生物入侵的监测、控制与管理难度相对较大。我国对陆地外来生物的入侵已开展了较为深入的研究,但对于海洋外来生物的入侵研究仍处于起步阶段,对其入侵监测、入侵机制、入侵危害的程度以及防治等问题缺乏基础数据。本文在分析国内外海洋外来生物入侵现状的基础上,概述其入侵生态学研究形势及相关成果,包括海洋外来物种的入侵途径、入侵过程、入侵生态效应以及全球变化对入侵的影响等。海洋外来生物的入侵可能对海洋生态系统造成直接或间接的影响,如种间竞争破坏生态环境、与土著种杂交造成遗传污染、病原生物及有毒藻类导致海洋生态灾害加剧等。此外,从政策和法规、入侵风险评估、监测和公共宣传教育、生物信息系统和有效管理机制等方面提出对我国海洋外来物种入侵的防治策略。本研究为我国海洋外来物种的进一步研究提供了参考。     

Marine Biodiversity in Japanese Waters

To understand marine biodiversity in Japanese waters, we have compiled information on the marine biota in Japanese waters, including the number of described species (species richness), the history of marine biology research in Japan, the state of knowledge, the number of endemic species, the number of identified but undescribed species, the number of known introduced species, and the number of taxonomic experts and identification guides, with consideration of the general ocean environmental background, such as the physical and geological settings. A total of 33,629 species have been reported to occur in Japanese waters. The state of knowledge was extremely variable, with taxa containing many inconspicuous, smaller species tending to be less well known. The total number of identified but undescribed species was at least 121,913. The total number of described species combined with the number of identified but undescribed species reached 155,542. This is the best estimate of the total number of species in Japanese waters and indicates that more than 70% of Japan''s marine biodiversity remains un-described. The number of species reported as introduced into Japanese waters was 39. This is the first attempt to estimate species richness for all marine species in Japanese waters. Although its marine biota can be considered relatively well known, at least within the Asian-Pacific region, considering the vast number of different marine environments such as coral reefs, ocean trenches, ice-bound waters, methane seeps, and hydrothermal vents, much work remains to be done. We expect global change to have a tremendous impact on marine biodiversity and ecosystems. Japan is in a particularly suitable geographic situation and has a lot of facilities for conducting marine science research. Japan has an important responsibility to contribute to our understanding of life in the oceans.     

The effects of protection from fishing on species richness: distinguishing between alternative explanations

Marine reserves that prohibit fishing often result in greater densities of individuals and more species than adjacent fished areas. However, simple conclusions about their effects on species richness are confounded, because more species are expected to occur wherever there are more individuals. Here, there is an important distinction between the number of species per sampling unit (species density), and species richness measured as the number of species per given number of individuals. When conservation of species richness is an important goal, analyses need to discriminate between the alternative explanations for differences in the number of species. We used rarefaction to test whether species richness was higher in two ‘no-take’ marine reserves after controlling for differences in the density of individuals. We surveyed each reserve in three different years. There was a higher density of individuals and species in each reserve than in adjacent fished areas. However, rarefaction analyses indicated that effects on species richness were weak after controlling for the number of individuals: slightly higher species richness was recorded inside each reserve in one of three surveys, but the difference was small, and was apparent only when the maximum number of individuals was approached. Our results therefore indicate that patterns in species density were not reflected by patterns in species richness—the application of rarefaction methods is needed to determine the responses of species richness to protection elsewhere. The distinction between species density and species richness will not be important in all situations, but when it is important, inferences about species richness cannot be reliably deduced from measurements of species density.     

Assessing biodiversity with species accumulation curves; inventories of small reptiles by pit‐trapping in Western Australia

Abstract We examined 11 non‐linear regression models to determine which of them best fitted curvilinear species accumulation curves based on pit‐trapping data for reptiles in a range of heterogeneous and homogenous sites in mesic, semi‐arid and arid regions of Western Australia. A well‐defined plateau in a species accumulation curve is required for any of the models accurately to estimate species richness. Two different measures of effort (pit‐trapping days and number of individuals caught) were used to determine if the measure of effort influenced the choice of the best model(s). We used species accumulation curves to predict species richness, determined the trapping effort required to catch a nominated percentage (e.g. 95%) of the predicted number of species in an area, and examined the relationship between species accumulation curves with diversity and rarity. Species richness, diversity and the proportion of rare species in a community influenced the shape of species accumulation curves. The Beta‐P model provided the best overall fit (highest r²) for heterogeneous and homogeneous sites. For heterogeneous sites, Hill, Rational, Clench, Exponential and Weibull models were the next best. For homogeneous habitats, Hill, Weibull and Chapman–Richards were the next best models. There was very little difference between Beta‐P and Hill models in fitting the data to accumulation curves, although the Hill model generally over‐estimated species richness. Most models worked equally well for both measures of trapping effort. Because the number of individuals caught was influenced by both pit‐trapping effort and the abundance of individuals, both measures of effort must be considered if species accumulation curves are to be used as a planning tool. Trapping effort to catch a nominated percentage of the total predicted species in homogeneous and heterogeneous habitats varied among sites, but even for only 75% of the predicted number of species it was generally much higher than the typical effort currently being used for terrestrial vertebrate fauna surveys in Australia. It was not possible to provide a general indication of the effort required to predict species richness for a site, or to capture a nominated proportion of species at a site, because species accumulation curves are heavily influenced by the characteristics of particular sites.